The invention concerns an apparatus for printing on individual articles, more particularly individual articles which are dimensionally stable, for example for decorating the articles, such as for decorating bottles of glass or plastic material, for instance using a screen printing process.
The use of modern printing inks which are at least substantially free from environmentally harmful constituents and which are hardenable for example by means of UV-radiation, in which respect attention may be directed for example to U.S. Pat. No. 5,985,376, is giving rise to a demand for printing machines and in particular screen printing machines which offer a very high level of through-put capacity.
As in future light glass bottles and in particular light glass bottles for drinks will be used to an ever increasing extent, it is not always possible for the bottles to be provided with register marks in the form of recesses, more particularly in the bottom of the bottle or at the edge of the bottom of the bottle, for the engagement therein of some form of register member such as register pins so that the article can be oriented and aligned in a specific fashion in the peripheral direction thereof, for example within a holder for carrying the article in a printing machine. Such specific orientation is required in particular when, as is the usual practice in particular when employing multi-color printing, a plurality of partial print images are successively applied to the article by the printing procedure, so that after the printing procedure is concluded the plurality of partial print images supplement each other to form the overall print image.
An object of the present invention is to provide an apparatus for printing on individual articles such as bottles, in which the article can be satisfactorily brought into a defined angular position in a holder for carrying the article and remains in that angular position throughout the entire operational passage through the apparatus, whereby there is then no longer any need for a renewed procedure for bringing the article into the correct registration relationship.
Another object of the present invention is to provide an apparatus for applying decoration to dimensionally stable individual articles by a printing procedure with which the movement of a holder for an article can be executed while passing through the machine in an accurately controllable and thus also accurately definable manner to afford a high-quality printing result.
A further object of the present invention is to provide an apparatus for printing on dimensionally stable individual articles which is of such a design configuration as to provide a high degree of accuracy in its operating movements and therewith a high level of quality in terms of the resulting print image in particular when implementing a multi-color printing procedure.
In accordance with the principles of the present invention the foregoing and other objects are attained by an apparatus for printing on dimensionally stable individual articles, for example for applying decoration thereto, comprising a continuously circulating transport means for transporting the articles along a transport path, each article being carried by a respective holder. The transport path has in operative association therewith at least one treatment station and at least first and second transfer stations. One of the transfer stations is in the form of a feed station in which the articles to be printed upon are fitted on to or into holders transported by the transport means. The other of the transfer stations is in the form of a removal station in which the printed articles are removed from the holders. During the printing operation the article is rotated about its longitudinal axis by suitable means in a first direction determined by the printing procedure and the transport direction, and after termination of the printing procedure the article is rotated back into its initial position by a rotation thereof about its longitudinal axis in a second direction opposite to the first direction.
As will be seen in greater detail from a description hereinafter of a preferred embodiment of the apparatus according to the invention, an article to be printed upon executes rotary movements in reciprocating manner about its longitudinal axis, which rotary movements may be 360xc2x0 or possibly even somewhat more. The arrangement of the apparatus is such that the rotary movement in a first direction takes place during a printing procedure in which the article is for example being rolled against a screen printing stencil. After termination of the printing procedure the article is rotated back into its initial position again, by rotation about its longitudinal axis in a second direction opposite to the first direction. In dependence on the arrangement of the individual treatment stations along the transport path, during that second rotary movement, the article can also pass through a drying station, for example and preferably a UV-station, in which case the printing ink which has just been applied to the article for example for decoration purposes thereon is at least dried and set to such an extent that a further partial print image can be applied to the article, without that adversely affecting the quality of the first partial print image already thereon.
In accordance with a preferred feature of the invention the article holders or receiving means provided by the holders for receiving the articles are rotated by way of a pivotably mounted toothed element which is movable with the respective holder and which is in engagement with a gear fixed to the above-mentioned receiving means, wherein that toothed element is provided with a cam roller engaging into a first cam which is mounted to the machine frame structure and the configuration of which is so selected that during the movement of the holder along the transport path along which the cam also extends, the article is caused to perform the above-indicated rotary movements about its longitudinal axis. Cams of that kind can be implemented with an extremely high degree of precision, while in the case of an endless cam in which the cam roller always remains in operative engagement with the cam, this also ensures that the holder and therewith the article secured therein are maintained in a position which is properly definable and controllable at any location on the transport path.
On the other hand the use of a cam with cam rollers makes it possible not to rotate the article in given portions along the transport path in the apparatus. That can be achieved without entailing particular expenditure by virtue of the cam extending substantially parallel to the transport path in the respective sections in which the article is not to be rotated. That will be desirable for example in the regions of the transport path, in which the articles to be printed upon are introduced into the apparatus or in which the articles with printing thereon are to be removed from the apparatus. In both cases such a transfer procedure can be carried out more easily if the holders are not rotating.
The reciprocating rotary movement of the articles with their holders is advantageous in particular when dealing with articles which have projection portions or the like protruding laterally beyond the contour of their body portion, for example handles or gripping configurations, as such projecting portions, upon a rotary movement which takes place only in one direction, require space which is not available in the majority of cases. At any event there is the possibility that the articles are properly oriented and aligned during the feed transport thereof to the apparatus, for example when being transported on a conveyor belt or in a transfer procedure, in dependence on the position of the above-mentioned handle or, if the article does not have such a handle, for example also in dependence on the position of a seam on the outside surface of the article, so that, upon being fitted into their respective holders, the articles assume in relation thereto a defined angular position in the peripheral direction, which is then maintained throughout the movement of the articles through the treatment stations.
In a further aspect of the invention the foregoing and other objects are attained by an apparatus for printing on dimensionally stable individual articles including a continuously circulating transport means for transporting the articles each carried by a respective holder along a transport path, the transport means comprising an odd number of holders for the articles, and further including at least first and second printing stations such as screen printing stations and a drying station downstream of the two respective printing stations in the transport direction. In each passage of the articles through the transport path, printing is effected only in one of the at least first and second printing stations disposed upstream of the common printing station, and the printing stations in which an article is printed upon during a circulatory movement are at a spacing from each other which is an even multiple of the spacing of two adjacent receiving means for receiving articles in the holders, in the transport direction. The spacing between first and second printing stations which in the transport direction are arranged upstream of a common drying station is an odd multiple of the spacing of two adjacent receiving means.
As will be further seen from the description hereinafter of a preferred embodiment, the arrangement as set forth in the preceding paragraph in respect of the printing stations and the drying stations affords the advantage of a lower level of capital investment costs as there is no need for a particular drying station to be arranged downstream of each printing station which for example may typically be a screen printing station. In addition, in terms of its utility, this apparatus affords an increased degree of flexibility as it is possible for example to provide an article with multi-color printing thereon, with the number of colors or inks used in the printing operation corresponding to the number of printing stations with which the apparatus is provided. On the other hand it is possible to use the apparatus for printing on articles with a respective print image comprising a plurality of partial print images, the number of which corresponds for example to half the number of printing stations in the machine. In this respect, in comparison with the first use, it would be possible to achieve double the output, in relation to the number of articles printed per unit of time.
Further objects, features and advantages of the invention will be apparent from the description hereinafter of a preferred embodiment of the invention.